【作者】 杨慧；

【导师】 陈普会；

【作者基本信息】 南京航空航天大学 ， 飞行器设计， 2012， 博士

【摘要】 颗粒增强复合材料在当今工程界得到越来越广泛的应用。随着增强颗粒尺寸的减小，复合材料的一系列宏观性能会发生显著的改变。深刻理解其内在的颗粒尺寸效应将对复合机理的认识和工艺设计起到重要作用。本论文着重开展以下研究工作：(1)利用有限元方法研究非均匀界面相对复合材料有效剪切模量的影响。着重研究界面相厚度，界面性能变化规律，边界条件和颗粒体积含量对有效剪切模量的影响。(2)基于Mori-Tanaka方法，提出一个可研究规则分布颗粒增强复合材料有效弹性性能的力学模型。在模型中，考虑粒子间相互作用及其特征分布，利用几何对称性求解应变格林函数，并通过引入双夹杂理论来描述界面相效应，从而得到等效弹性常量的显式表达，并与上一章的有限元数值结果对比，以验证该模型的准确性。(3)从一个全新的角度来解释颗粒尺寸效应对聚合物基复合材料力学性能的影响。基于分子链网络理论，将颗粒看作分子链之间的缠结，类似聚合物分子链中的物理缠结或化学交联，从而提出一个可用于研究聚合物基复合材料颗粒尺寸效应的分析模型。(4)基于Eshelby等效夹杂理论和Mori Tanaka方法，建立一个高弹性基复合材料的细观力学模型。该模型基于单一分子链模型建立，可分析纯橡胶材料和复合材料的力学特性，并通过与实验数据进行比较来验证模型的准确性。(5)提出一个可描述颗粒增强复合材料的渐进式脱粘损伤、基体塑性及颗粒尺寸效应的本构模型。采用双夹杂模型将脆性界面相嵌入到增量损伤理论模型，用界面分离的能量平衡式来描述渐进式脱粘损伤。该模型可研究颗粒尺寸效应和界面性能对复合材料应力-应变关系的影响，并可解释界面相对复合材料力学性能的颗粒尺寸效应的影响。(6)在增量损伤理论中考虑韧性界面的作用，研究颗粒尺寸对颗粒增强复合材料弹塑性损伤行为的影响，并应用场波动方法确定基体与界面的等效应力。该模型可研究渐进性脱粘损伤、颗粒尺寸效应及界面相性能对颗粒增强复合材料的有效应力-应变关系的影响。由于韧性界面相的存在，颗粒增强复合材料中应力传递和屈服起始变得更加复杂，则应用有限元方法研究韧性界面对应力传递和和屈服起始的影响。更多还原

【Abstract】 The thesis is to interpret the particle size effect on the equivalent stiffness and plasticbehaviors of composites from different point of views. Based on the inherentmicrostructures of composites, some innovative methods are developed. The basicresearch contents are as follows.(1) Numerical studies on the effective shear modulus of particle reinforced composites withan inhomogeneous interphase are systematically performed. The influences ofinterphase thickness, variation laws of interphase properties, boundary conditions andparticle volume fraction on the equivalent shear modulus are carefully investigated, andthe accuracy of the existing models is verified.(2) A micro-mechanics model is developed to study the effective elastic properties ofcomposites reinforced by regularly distributed particles. Particle interaction anddistribution are simultaneously taken into account by using strain Green’s function,which is determined by utilizing the conditions of geometric symmetry. TheDouble-Inclusion configuration is introduced to describe the role of the interphase.The overall elastic properties are described by three independent elastic constantsexpressed in the explicit form.(3) Particle size effect is attributed to the synergism mechanism between particles andthe host matrix. A molecular-chain-network based micromechanics model waspresented for exploring particle size effect on the effective modulus. In the presentmodel, particles are regarded as junctions among molecular chains, which areequivalent to the cross-links pre-existing in the polymer. At a certain particleconcentration, the smaller the particle size, the higher is the cross-link density in thecomposites, and the higher is the effective stiffness of the resulting composites.Therefore, particle size effect would be clearly demonstrated from a new point ofview, which is different from all the existing explanations.(4) A micromechanics–based model is proposed for the finite strain deformation offilled elastomers based on generalized Eshelby’s tensor and Mori Tanaka’s method.The present formulation leads to a clear explanation of the constraint effect ofrubber–like matrix on the inclusions. Comparisons with experiments and other micromechanics models are conducted. It is observed that an improvement inpredictive capability for the composite with randomly dispersed particles wasachieved by the present method. Based on the latest experiment of single molecularchain, a compact network model is fatherly developed to reflect the microstructureeffect on the stress–strain relations of rubbery polymer and the resultingcomposites.(5) An incremental damage model of PRC has been extended to three-phase compositesfor interpreting particle size effect. The interphase was perfectly incorporated as athird phase with the help of double-inclusion model. Progressive damage wascontrolled by a critical energy criterion. Based on the developed model, particle sizeeffect on the mechanical behaviors of composites was clearly interpreted from therole of the interphase, which is different from all the existing researches.(6) A new micromechanics model of particulate reinforced composites was proposedto describe the evolution of debonding damage, matrix plasticity and particle sizeeffect on the deformation. A ductile interphase was involved to analyze thedependence of elastic plastic damage behavior on particle size. The equivalentstresses of the two constituents were determined by field fluctuation method.Furthermore, a unit cell (UC) based FEM was used to understand their evolutionand demonstrate the role of the interphase.更多还原